JPH0244006B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to a plurality of strap-down force rebalancing gyroscopic rate sensing devices for measuring the rate of rotation of an aircraft about a main axle. It relates to a gyroscope reference device of the type included with a device for calculating stabilization and attitude data of an aircraft. A typical strap-down device is an aircraft strap-down attitude and heading reference device that uses a skew-axis two-degree-of-freedom rate gyro.
Reference System for Aircraft Employing
Skewed Axis Two Degrees of Freedom Rate
No. 4,212,443, assigned to Sperry Corporation. More particularly, the present invention relates to an improved torque feedback control system for a two degree of freedom rate sensing system.

2 Description of the Prior Art Strap-down gyroscope inertial reference systems for aircraft and spacecraft are well known to those skilled in the gyroscope aircraft controller art, and many rate gyro configurations and controls based thereon are widely described in the literature. There is. Such devices typically include a plurality of rate sensing devices strapped to the vehicle to measure the vehicle's angular velocity about its principal axis, which measurements are fed into a digital computer along with vehicle acceleration and heading measurements. Generates output data used for aircraft stabilization, control, navigation, or guidance. Since the gyro is strapped to the fuselage, the rate sensing device is preferably of the force or torque rebalancing type. That is, the gyro is kept substantially aligned with its supporting case by feeding back the gyro pick-off signal to the gyro torquer in a manner that maintains its signal value at substantially zero, and the torquer current required to do so is applied to the rate gyro. It is therefore a measure of the rate being sensed. Typical two-degree-of-freedom rate sensing devices of this type are U.S. Pat.
CGBuckley, JA, published February 26, 2017
U.S. Patent No. 4,189,948 by Kiedrowsky, “Permanent Magnet Torque for Free Rotor Flexure Suspended Gyroscopes”
Torquer for Free Rotor Flexure Suspended
Gyroscopes), and both inventions are assigned to the Sperry Company. It will be appreciated that the final output of the gyroscope rate sensing device must meet the requirements of available digital computer technology.

A device that generates the output of a gyroscope rate sensing device compatible with a digital computer was introduced in September 1980.
Transferred to Sperry Co., published on the 16th.
U.S. Patent No. 4,222,270 to Arnold R. Allen, Gyroscope Rate Range Switching and Control
control system). The Allen patent discloses a pulse-width modulation type analog-to-digital switching device useful in a strap-down inertial gyroscope reference device that uses a plurality of force-balanced gyroscope rate sensing devices to sense aircraft rate about the main axis. where the gyrotorque feedback current is kept precisely proportional to the sensed aircraft rate, and a precision digital count proportional thereto is desired. The present invention incorporates a digital counting technique that generates a precision digital count that is proportional to the current applied to the torquer. Such counts are generated by using a high frequency clock to quantize a pulse width modulated low frequency square wave proportional to the amplitude of the corresponding gyroscope error signal; Determine the magnitude of the nulling feedback current applied to the gyrotorca coil. Unidirectional digital counters are operated synchronously by the same square wave and use the same high frequency clock to generate the counter clocking frequency so that the counter output corresponds to the current applied to the gyro torquer relative to the reference count. Hence the desired digital number corresponding to the sensing rate. The precision current applied to the gyro torquer is controlled by a VMOS power switching transistor circuit. The adverse effects of excursions associated with the rise and fall of pulse-width modulated square wave currents, especially at the positive and negative extremes, are eliminated by the use of guard band pulse pairs at the beginning and end of the modulator duty cycle; The pulses are used predictively to control the rise and fall of the torquer current and blank the counter to eliminate uncertainty in counting switching times and ensure that irregular torque transients are not applied to the torquer. Assure.

As detailed in the aforementioned Allen patent, the torquer input signal follows the gyroscope off signal (within a 95% and 5% duty cycle by guard band pulses) to 1/ A series of 500 Hertz current pulses with modulated pulse widths varying from 2 positive and 1/2 negative to almost all positive and all negative. However, it should be noted that there is an undesired transformer-like coupling between the torquer coil and the pickoff coil, which has a detrimental effect on developing the net torque to be applied to the gyro rotor. This net torque results from the effects of the erroneous pick-off signal being nulled out and the rotor suspension spring constant and self-evacuation (windage, etc.) phenomena, thereby imparting unnecessary torque to the gyro and thus along with the rate input. This results in undesirable drift of the changing gyro. Furthermore, because of the close spacing between the torquer coils, if the pulse width modulator square wave fall of each channel of the gyro falls at or very close to the same time, the changing magnetic field of one pickoff coil will be transformer coupled to the other coil. Note that the input rate thus produces a distorted pulse width waveform and undesirable bias drift.
Therefore, there is a need for a device that minimizes the transformer-like coupling that occurs in flexure-suspended gyroscopes of the type having pulse-width modulated torquer signals.

SUMMARY OF THE INVENTION The normal torque feedback operation of prior art flexure-suspended gyroscopes having pulse-width modulated feedback torque signals eliminates undesirable inductions, such as transformer-like coupling between the pickoff coil and the torquer coil; There is a transformer-like coupling between the torque coils themselves. Transformer-like coupling produces undesirably closely spaced bias drift outputs based on input angular velocity. The apparatus of the present invention provides a means for eliminating, and substantially eliminating, such undesired bias drift by minimizing undesired induction. To minimize transformer-like coupling between the pick-off coil and the torquer coil, the pick-off excitation frequency is chosen to be harmonically independent of the torquer coil frequency, so that the difference between an integer multiple of one frequency and the other frequency is It is about several hundred hertz or more. In order to minimize the transformer-like coupling between the narrowly spaced torquer coils themselves, the fall of the pulse of the pulse width modulation signal applied to the torquer coils is delayed from one side to the other to prevent the above-mentioned transformer-like coupling. Means are provided.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The apparatus of the present invention is operable in either high or low range modes to produce precise measurements of aircraft rate, and is suitable for use in an aircraft's digital strap-down attitude and heading reference system. Used to convert values into digital data. The rate gyroscope of such a device may be a twin-axis torque feedback flexure suspended gyroscope of the general type described in the disclosures of the above-mentioned patents; A flexible rate gyroscope is disclosed. Such a gyroscope actually has a gyroscope rotor freely suspended by a flexible support member and rotated about an axis of rotation by an electric motor drive shaft mounted within the instrument casing. It is characterized by Free tilting of the gyroscope rotor about a pair of axes perpendicular to the normal axis of rotation is made possible by the flexure support.

Such gyroscope instruments are usually provided with a pair of 90 degree spaced inductive pickoffs which detect the angular displacement of the rotor relative to its axis of rotation about mutually perpendicular axes of inertia. Cooperative orthogonally spaced pairs of similarly arranged torque coils are also typically provided. In FIG. 1, the gyroscope and its coil are shown schematically for convenience, and the torquer coil pair is each single torquer coil 34a, 34b,
A pair of induction pickoff coils is shown with each single pickoff coil 33a, 33b. Normally, for example, the signal from the pick-off coil 33a is sent to the buffer amplifier 3.
2a and finally to the torquer coil 34a to perturb the gyroscope rotor 41 in opposition to the preset caused by the input rate, so that the axis of the rotor 41 is Remain substantially aligned with a motor casing (not shown) attached to the aircraft. As described in the aforementioned patent, rotor 41 is flexibly mounted on the drive shaft and rotated by a motor within the instrument casing. In a similar manner, the signal from the right angle pick-off coil 33b is sent to the buffer amplifier 3.
It finally flows into the torquer coil 34b through the gyro restoring loop provided with 2b and is zeroed out. It will therefore be seen that the current driven into either torquer coil 34a or 34b is proportional to the rate at which the gyroscope casing is rotated as the aircraft itself rotates correspondingly about its respective axis of inertia. For example, when an aircraft to which a gyroscope is fixed rolls, the gyroscope rotor 41 moves against its casing by perturbing the rolling rotor 41 at the same rate as the aircraft is rolling. and held substantially fixed. Therefore, if the current flowing through the corresponding torquer coil 34a or 34b is accurately measured, for example, the roll rate of an aircraft can be accurately measured.

In the following it will be clear to those skilled in the art that the control devices associated with each of the two axes of inertia are functionally identical. A gyroscope rotor position restoring system comprising loop 1a uses the tilt signal generated for one axis by pickoff coil 33a to provide a preset signal to torquer coil 34a for the corresponding axis via line 30a. Similarly, the gyroscope rotor righting loop 1b uses the tilt signal generated about the orthogonal axis by the pick-off coil 33b to
A preset signal is provided to the right angle shaft torquer coil 34b via the terminal 34b. It will be clear that since the two cooperating loops 1a and 1b are similar, only loop 1a needs to be described in detail.

FIG. 1 is a simplified block diagram of an apparatus employing the present invention, and this description will be an important aid in discussing the details of the invention as further discussed in connection with FIG. The error signal detected by pickoff coil 33a is coupled to a set of inputs of demodulator 2a via buffer amplifier 32a. Like the demodulator 2b, the demodulator 2a is supplied with a constant amplitude reference rectangular wave having a frequency of, for example, 9.708 kHz from the power supply 10a, and this is applied to the pick-off coil 33.
It is also an excitation signal for a and 33b. The gyro drive motor may be driven from a 400 hertz signal source (not shown). The variable polarity DC output error signal of the demodulator 2a is passed through a conventional filter and waveform shaping circuit 3.
a, is coupled to one input of amplifier 7a via variable gain amplifier 6a and resistor 42a. Similarly, the variable polarity DC output error signal of demodulator 2b is similarly coupled to one of amplifiers 7b via filter and waveform shaping circuit 3b, variable gain amplifier 6b and resistor 42b. As mentioned in the above application, if the gyroscope axis is oblique to the machine axis to increase stability, the error signal output of the demodulators 2a, 2b is first accompanied by a filter and waveform shaping circuit. It can be seen that conventional cross-axis compensation processing can be applied. This process is not necessarily related to the present invention and will not be described. For example, further with respect to loop 1a, the output of demodulator 2a is provided as one input of amplifier 7a, ie, an amplifier connected as a conventional comparator, and the first input level is transmitted from power supply 8 (described later) via resistor 43a to the first input level of amplifier 7a. Compare the instantaneous level of a repeating ramp or sawtooth voltage coupled to two inputs. This sawtooth wave has a 500 hertz repetition frequency in the illustrated embodiment and is provided by a timing circuit generally designated 5.

The output of the comparator 7a is the feedback resistor 44.
a, a novel compensation circuit comprising a capacitor 40b and a resistor 41b, and a pulse modulator 9a, which modulation circuit is connected to terminal 10b of timing circuit 5.
It is also provided by a clock source (not shown) coupled to the clock. In the embodiment shown, the clock pulse is
It is applied at a rate of 100 kilohertz and is used to quantize a pulse width modulated square wave as described in more detail below. The output of circuit 9a serves two purposes. This output is applied directly via line 14a to a switching device 17a, here designated as an H switching device, and this signal determines the conducting and non-conducting states of the individual element switches making up the signal switching device 17a. The H-switching devices 17a and 17b are provided with suitable reference inputs 16a and 16b coupled to a unidirectional voltage source (not shown) which, under control of the signal on line 14a, connects the gyrotorque coil 34a and Provides a torque current source to be applied to 34b.

The output of the pulse width modulator 9a is also provided to a counter-decoder 21a, the second input of which is provided with counter control pulses from the counter controller 20 of the timing circuit 5. Counter 21a periodically counts the quantized pulses corresponding to the analog rate signal of loop 1a and is controlled by a computer input interface, e.g., in a conventional digital computer (not shown) coupled to the output of counter 21a. Such data is retained for future reference. Note that counter 21a is a simple unidirectional counter and the clock pulses are counted only during the positive portion of the quantized square wave as described below. Thus, the reference count on terminal 22a, which corresponds to half of the total count representing the sawtooth duty cycle, is the counter
Applied to decoder 21a, the measured count is subtracted from a reference count to produce a count proportional to the sensed aircraft rate. Alternatively, the decoder portion of counter-decoder 21a is used to determine the rate range mode of operation of the present invention.

According to the present invention, guard band pulses from pulse source 15 synchronized to a 500 Hertz duty cycle are generated to provide precise control of the current provided by H-switching device 17a and counter 21a.
A corresponding fine control of the quantization pulses applied to the quantization pulses is performed. These pulses compensate for inaccuracies otherwise associated with the finite rise and fall times and possible overshoot characteristics of the torquer current, and ensure that the pulses applied to the counter faithfully represent the effective current applied to the gyro torquer. used to ensure that. The inclusion of guard band pulses provides a synchronized interval to the 500 Hertz duty cycle during which the control loop should switch from low rate mode to high rate mode by decoder 21a responsive to the counter contents. or vice versa, which in turn determines whether the high current source or the low current source is switched by the H switching device 17a. This is illustrated schematically in FIG. 1 by line 19a connecting counter decoder 21a and providing a high/low mode command to the H switching device. Also line 1
The high/low signal on 9a also controls the gain of the gyroscope off signal via variable gain amplifier 6a to ensure that the overall closed loop gain and loop stability remain the same in both modes of operation.

Pick-off coil 33b and torquer coil 3
The loop 1b associated with 4b is the gyro rotor 4
1 and its cooperation are substantially identical in construction and operation to those associated with loop 1a, pick-off coil 33a and torquer coil 34a, and therefore require no further detailed explanation. For example, the H switching device 17b
b and 19b, the latter determining whether a low range or high range torque signal is applied to torquer coil 34b. Further, the counter decoder 21 periodically accumulates the counts corresponding to the analog rate signal of the loop 1b, and accumulates the counts to stabilize the aircraft.
The counts are rate range decoded and sent to a digital computer or other data processing device for conventional use in control, navigation or guidance.

As mentioned above, low cruising range is the normal mode.
The diagonally opposite switch elements of the H-switcher open and close simultaneously and instantaneously according to each positive and negative region of the pulse width modulated square wave as controlled by the signals on lines 14a and 14b. . For example, if the input rate signal to comparison amplifier 7a is zero, diagonally opposite switches of H-switching device 17a will be in a conducting and non-conducting state for equal lengths of time.
Therefore, the net torque applied to the gyro torquer 34a becomes zero.

As detailed in the above Allen characteristic, the torquer input signal follows the gyroscope off signal (within 90% and 10 duty cycles by guard band pulses) to 1/2 positive and 1 A series of 500 Hertz current pulses with widths varying from /2 negative to nearly all positive and all negative. It has been found that when the frequency of the pick-off signal is an integral multiple of the torquer frequency, there is a harmonic transformer-like coupling between the torquer coils 34a, 34b and the pick-off coils 33a, 33b. Furthermore, the close proximity of torquer coils 34a, 34b creates a transformer-like coupling between themselves. From the torquer coils 34a, 34b to the pick-off coils 33a, 3
The harmonic transformer-like coupling to 3b has a detrimental effect on generating the net torque to be applied to the gyro rotor 41, which is nullified by the erroneous pick-off signal and the rotor suspension spring constant and automatic discharge. arises from the action of phenomena. Therefore, unnecessary torque is imparted to the gyro rotor 41, thus creating an undesirable gyro drift that varies with rate input. Torque coils 34a, 34b and pick-off coil 33
The harmonic transformer-like coupling between a and 33b and the transformer-like coupling between the torquer coils themselves are represented by dotted arrows in FIG. Torca coil 34a,
34b and pick-off coils 33a, 33b and the very small dimensions of the flexure-suspended gyroscope attempt to provide shielding that may otherwise alleviate transformer-like coupling. becomes physically impossible.

However, the harmonic coupling described above between the torquer coils 34a, 34b and the pickoff coils 33a, 33b can be effected by selecting the frequencies of the torquer excitation signal or the pickoff excitation signal such that there is no effective harmonic relationship between them. can be removed. In this embodiment, the pickoff excitation signal is selected to have a frequency that is a desired non-integer multiple of the frequency of the torquer excitation signal. Preferably, the difference between an integer multiple of the torquer frequency and the pickoff frequency is on the order of several hundred hertz or more.

The operation of the device of FIG. 1 can therefore be controlled by the high frequency main clock device 50 of FIG.
The various frequencies required by the various components of the system are generated by dividing the main clock frequency using conventional frequency divider circuits 51 and 52. As shown in FIG. 3, the main clock unit 50 operates at 4 MHz and the 500 Hz torquer frequency is generated by dividing by 8000 by frequency divider 51. Note that in the prior art Allen patent, the frequency of the pick-off excitation signal is 10 kilohertz, which is an integer multiple of the 500 hertz torquer frequency. However, in the present invention, the frequency of the pickoff excitation signal is selected to be approximately 9.708 kHz, which is generated by frequency divider 51 by dividing the 4 MHz main clock frequency by 412. Note also that 9.708 kilohertz is also used as the reference frequency for demodulators 2a and 2b. in prior art
500 hertz torquer square wave demodulators 2a and 2b
The harmonic coupling to caused the pickoff output signal to generate a bias at the demodulator output, which tended to drive that output to zero via the feedback loop. This zeroing of the demodulator output produced a resulting bias drift based on the corresponding steady state torque and input angular velocity on the gyro. However, as the pickoff and demodulator excitation frequency
By selecting 9.708 kHz, the torquer coils 34a, 34b and the pick-off coil 3
These undesired bias drift effects associated with inductive or transformer coupling between 3a, 33b are eliminated.

As mentioned above, there is also a transformer-like coupling between the torquer coils 34a and 34b via the rotor shell and gas. This second transformer coupling can be attributed to the proximity of the torquer coils 34a, 34b and the precisely shaped pulse width modulated torquer signal. As described in the Allen patent, the pulse width modulated feedback or rebalanced torquer signal is essentially a H switching device 17a, 1.
5 according to the gyroscope off signal via 7b.
It is a very precise shaped square wave current pulse whose pulse width varies between % and 95% duty cycle. Furthermore, since these pulses are generated from a common logic circuit, each torquer coil 34a
The rises of the pulses applied to 34b always rise exactly at the same time. However, their falls occur at variable times based on the pickoff signal.

Note that the A channel pickoff coil 33a energizes the A channel torquer coil 34a and the B channel pickoff coil 33b energizes the B channel torquer coil 34b. However, conventional gyro preset theory states that the rotor must be torqued about the gyro's Y-axis in order to nullify the pick-off signal generated by the tilt of the rotor 41 about the gyro's X-axis. I want to be understood.

Sometimes the A and B current pulse widths are quite different,
That is, the pulse edges do not fall at the same time, that is, the pulse edges do not overlap in time. Therefore, for example, when the falling edge of the B torquer square wave is falling, the A torquer square wave is completely positive or completely negative. According to classical transformer theory, the changing current in the B torquer coil 34b does not couple to the A torquer coil 34a because its maximum current is already flowing. However, for other combinations of aircraft roll and pitch angular velocity, the falls of the A and B square waves both fall very close together or overlap. When this occurs, the magnetic field generated by the change in current in the torquer coils 34a, 34b is mutually coupled from one torquer coil to the other so that the magnetic field induced in either one during the rise of the pulse is equal in magnitude and opposite in direction. The current induces a current that is not compensated for by the current and thus introduces a gyro bias drift rate. In other words, the pulse waveform is distorted. The present invention overcomes these undesirable torquer coil cross-coupling effects and thus eliminates the resulting gyro bias drift based on input angular velocity. Essentially this is done by deliberately preventing both falling edges from always occurring at or about the same time. This is done by detecting the beginning of the falling transition of one pulse and immediately delaying the beginning of the other transition. The amount of delay is approximately equal to the normal pulse falling transition time.

FIG. 1 shows one embodiment of novel pulse width modulation compensation circuits added to a prior art torque rebalancing device, and FIG. 2 shows the pulse width modulation waveforms associated with the addition of these circuits. As shown in FIG. 1 and described in the prior art Allen patent, a sawtooth voltage is applied to comparator amplifiers 7a and 7b which also provide a demodulated gyroscope off signal. For now, considering only the A channel of the gyro and referring to FIGS. 1 and 2, it is assumed that the aircraft is experiencing a turn rate in the direction that causes the signal to be generated by the pick-off coil 33a. Demodulator 2a and amplifier 6a operate in response to this signal to generate a finite direct current signal at the input onto high gain comparison amplifier 7a. When the sawtooth voltage at the input below amplifier 7a increases to a value equal to the pickoff signal, amplifier 7a outputs a large switching voltage to pulse width modulator 9a. As described in the Allen patent, this provides a proportional current pulse width signal (500 hertz frequency) to the A channel torquer coil 34a via the H switching device 17a and a resultant proportional torque and pick-off signal on the gyro rotor 41. The result is a synthetic preset that tends to reduce . As the error signal decreases toward zero, the positive pulse width becomes progressively narrower until a zero pick-off signal causes the torquer coil to again be half in one direction and half in the opposite direction, resulting in zero net torque on the gyro rotor 41. The aircraft is A
The same motion occurs when experiencing a rate of rotation about an axis. Note that both torquer signals are generated from a common sawtooth reference voltage source 8.

As mentioned above, if the falling edges of the 500 Hz torquer current pulses fall at approximately the same time, that is, if there is an overlap in the pulse falling time, the first-four falling current to either the torquer coils 34a or 34b is of the transformer type, that is, mutual inductance coupling. to the coil of the other torquer, so that when its trailing current begins to fall, the coupled current changes the latter, effectively increasing or decreasing the net current therein. Conversely, the second falling current changes the shape of the first-fall end depending on the mutual relationship. Obviously, a large number of such increased pulse cycles will result in an erroneous net torque on the gyro rotor 41 and an undesirable bias drift error. This phenomenon is particularly pronounced during low input angular velocities about one or both axes up to about ±5°/sec.

The present invention prevents this undesirable coupling by ensuring that the falling edges do not overlap. Referring again to FIGS. 1 and 2, comparator amplifiers 7a and 7b responsive to the gyro pick-off signal voltage and the sawtooth voltage are conventional high gain devices;
It is envisioned that the sawtooth signals essentially operate as switching devices that provide relatively large negative voltages at their outputs whenever they become more positive than the pickoff error signal. According to the invention, this DC voltage from the output of either comparison amplifier 7a, 7b of either channel is mutually applied to the sawtooth wave input of the other channel via coupling circuit means such as a pulse forming circuit. Preferably, the combination circuit comprises a differentiator circuit comprising a series connected capacitor resistor such as capacitors 40a, 40b and resistors 41a, 41b. The coupling circuit means is designed to generate a so-called blanking pulse having a time width approximately equal to the normal falling time of the falling edge of the variable width square wave.

The effect of this pulse applied mutually between the channels of the gyro is shown schematically in FIG. Assuming that the A channel comparator amplifier 7a is turned on first (the chances of it turning on at exactly the same moment in two comparators due to circuit tolerances and normal device operation are very small), its DC output will be The resulting DC pulse output from and applied through the axis circuit is applied to the sawtooth input of amplifier 7b in a direction that reduces the sawtooth voltage at the comparator input during the time width of the pulse. The output of comparison amplifier 7b is therefore delayed and the fall of the resulting rectangular wave current is suppressed to prevent the changing current of the A channel square wave from coupling to B channel torquer coil 34b. This same behavior occurs when the falling edge of the B channel wave occurs first. Those skilled in the art will appreciate that the waveforms in FIG. 2 are greatly exaggerated and that in reality the gyroscope off signal does not change as quickly with sawtooth frequency as shown. For example, in one embodiment, the sawtooth wave changes at 500 cycles per second, whereas the gyroscope signal typically changes at a few cycles per second.

Although the invention has been disclosed in conjunction with a preferred embodiment, other embodiments may be found useful by those skilled in the art. For example, instead of generating the blanking pulses using analog technology, they can also be generated using digital counter technology. The output of the comparator amplifier starts a digital counter which counts through a predetermined number of clock cycles to generate the desired delay time. Also, instead of the A and B channel pulse width modulators being controlled synchronously from a common sawtooth source, both channels may be controlled by suitably phase shifted sawtooth waves of the same frequency.

Although the invention has been described in its preferred embodiment, the terminology used is intended to be descriptive and not limiting, and it is to be understood that modifications may be made within the scope of the claims without departing from the true scope and spirit of the invention. I hope you understand that it is possible.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional twin-axis torque rebalancing rate gyroscope equipped with the improved pulse width modulated torque rebalancing device of the present invention, showing its basic components and their electrical interconnections. 2 is a graphical representation of relevant electrical waveforms useful in explaining the operation of the apparatus of the present invention, and FIG. 3 is a block diagram of a clock circuit for use with the apparatus of FIG. In the figure, 1a, 1b... gyroscope rotor restoring loop, 2a, 2b... demodulator, 3a, 3b...
Filter and waveform shaping circuit, 5... Timing circuit, 6a, 6b... Variable gain amplifier, 7a, 7b...
Comparison amplifier, 9a, 9b...Pulse width modulator, 17
a, 17b...Switching device, 21a, 21b...Counter decoder, 32a, 32b...Buffer amplifier, 33a, 33b...Pick-off coil, 34
a, 34b... Torque coil, 41... Gyroscope rotor, 50... High frequency main clock device, 5
1, 52... Frequency dividing circuit.

Claims (1)

Claims: 1. a free rotor rotating about an axis of rotation and adapted to tilt freely about a pair of mutually perpendicular sensing axes perpendicular to the axis of rotation in response to turning motion of the aircraft; pick-off coil means coupled to said rotor having an alternating current reference source connected thereto to detect tilt of the rotor about said sensing axis and provide a corresponding alternating current electrical signal accordingly;
torquer coil means also coupled to said rotor for imparting a torque thereon in accordance with an alternating current proportional to said pick-off signal to reduce said pick-off signal to zero so that the torquer current is proportional to the turning motion of said aircraft; in a gyroscope reference device for a navigable aircraft comprising at least one torque rebalancing two-degree-of-freedom gyroscope, comprising: compensating for electromagnetic coupling between torquer coils effective about adjacent axes; and pulse width control means comprising comparison means responsive to said pick-off signal and sawtooth reference voltage for providing a corresponding substantially square wave current pulse train to one of each of said torquer coil means. Each of said square waves has one end whose occurrence time can vary according to the amplitude of said pick-off signal, and said time varying one end of said respective square wave pulse train is responsive to each of said comparison means. and circuit means for preventing two ends from substantially coincident. 2. The apparatus of claim 1, wherein an integer multiple of the frequency of said square wave torquer pulse train differs from the frequency of said pickoff reference source by a substantial amount to reduce electromagnetic coupling between adjacent pickoff coils and torquer coils. The above device is characterized in that it prevents. 3. The device according to claim 1, wherein the circuit means includes means for delaying the output of the other comparing means for a predetermined period in response to the output of the comparing means occurring first in time. The above device characterized in that: 4. The device according to claim 3, wherein the circuit means comprises capacitor means. 5. The device according to claim 3, wherein the circuit means comprises a resistor-capacitor circuit means. 6. The device according to claim 5, wherein the resistor-capacitance circuit comprises a series-connected capacitor and resistor means.